1. Field of the Invention
This invention relates to valves in piping, and more particularly, but not by way of limitation, to a valve which inflates into a fluid stream immediately stopping the fluid flow.
2. Description of the Related Technology
It is well known that valves of a large number of varieties and designs have been used for many years for a variety of purposes. Bladders used in some of the valves have been made of rubber and other materials to hold different liquids, depending on the application, cost, and weight considerations. Also well known in the art are expandable seals. These seals are flexible enough to be pressed against another structure for sealing, yet durable enough to withstand many expansions and contractions, again depending on application. The materials used in these seals differ depending on factors such as the type of gas, or liquid, coming in contact with the seals. Sometimes the fluids contacting the seals are corrosive or radioactive. Another factor influencing the selection of seal or bladder material for a particular valve application is the shelf life of that material when not in use.
One field of use involving a variety of valve types is in the aerospace field. For example, design requirements dictate using a shutoff valve for applications in rocket staging systems. Rocket staging systems can provide a variety of propulsion fluids for lifting payloads into space. Depending on the staging system design, one or more stages provide propulsion fluid, such as hydrogen or other rocket fuel, to rocket motors. Timing is critical to achieving liftoff of a launch vehicle, achieving orbit, and making minor corrections in trajectory. Therefore, any valve intended to shut off fluid flow to the engines must operate immediately and effectively. Otherwise, the fluid fuel provides unwanted additional propulsion. In addition to a need for a valve to effectively control fluid flow, it is critically important for valves to shut down under emergency situations. If a valve does not immediately close, lives may be lost because of explosions or inadvertent lift off.
Conventional aerospace shutoff valves have been used for years. These valves are typically of the ball or butterfly type. Two typical activating mechanisms used in aerospace shutoff valves for large diameter piping ducts are electromechanical or pneumatic. In an electromechanical system, the shutoff valve is typically motor driven. More typically, a pneumatic actuating mechanism would use a piston to cause a rack and pinion gear train to close the shutoff valve.
Problems with the above-described shutoff valves include undesirable weight penalties, because of the required metallic materials used. The shutoff valves are also complex in design. Added weight and design complexity result in increased system costs. Design complexity may also require additional backup systems because of single point failure concerns with particular components. Ideally, a design should be fail safe when safety is a prime consideration.
Other operating environments also require shutoff valves to prevent or stop catastrophes to people or equipment. For example, ocean recovery systems, explosive fluid and toxic fluid systems require immediate fail-safe shutoff valves.
With today's increased emphasis on safety, improved fail-safe devices are required. Additionally, the added costs of components, labor, and component replacement, and the unavailability of launch vehicles due to system failure have added significantly to launch system costs and loss of market share in commercial operations.
Therefore, over time, many attempts have been made to improve shutoff valves. Some of the attempts to address particular requirements and environments are explained in the following representative and pertinent prior art.
JONES U.S. Pat. No. 3,022,977, discloses a vacuum operated normally closed valve where an inflated bulb collapses. The valve of the reference is designed to prevent solid particles from flowing. The JONES valve is not normally open, nor is the JONES valve used to stop fluid flow.
KOSIK U.S. Pat. No. 3,128,078, discloses a gate valve with an expandable seal acting against an air cushion. A gate valve allows closing and opening of a space to either prevent or allow passage of a substance. KOSIK's valve is operated by a handwheel which may be turned in a clockwise direction to close the valve. Numerous metallic parts are used in this invention. The valve of the reference operates mechanically and is manually operated. One of the problems with the KOSIK valve is that it has numerous parts requiring manufacture, thereby creating additional weight, and therefore incurring additional costs. In addition to the problem of additional weight, the KOSIK valve is not suitable for handling situations where immediate flow stoppage is mandatory. The valve is also not convenient for use in large diameter piping or ducting because of the added force required for closing or opening. The complex design of the KOSIK valve suggests a relatively expensive system.
SAMOUR U.S. Pat. No. 3,159,377, discloses an inflatable bladder. One of its objects is to provide a stopper valve for piping used in the chemical industry. The SAMOUR valve needs to ensure perfect tightness and resistance to corrosive products at high temperatures. The bladder is closed by inflating it with a fluid. One of the problems with the SAMOUR valve includes being of a highly complex design because of the particularly stringent design requirements for handling chemically corrosive fluids. Therefore, the cost of manufacture is relatively high. The valve of SAMOUR also has an axially placed valve within the piping. Having a valve transversely in line with the fluid is a problem because the components are exposed to corrosive materials and, therefore, must be impervious to corrosion. In addition, an unacceptably high pressure drop occurs across the valve area because the valve is partially obstructing the flow of fluid.
JOHNSON U.S. Pat. No. 3,567,176, is of interest because it discusses a ball valve assembly wherein the ball member moves transversely within a pipe to close off the downstream end from the upstream end. The JOHNSON valve does not remain in one location within a pipe or duct. The valve ball is pre-loaded between annular seals. The valve is also pressed tightly against structure by internal fluid pressure. A secondary stem seal is provided as a backup mechanism should the axially corrugated tubular envelope which covers the valve stem fail. The JOHNSON valve is used in piping that must be permanently sealed, and carry corrosive, radioactive, or other dangerous and harmful fluids. One of the problems associated with the JOHNSON valve includes the complex nature of the design to meet the need to handle radioactive fluids. The components must have a very long life, and the sealing features must be fail safe. Therefore, costs for this valve system are relatively high.
MEHAFFEY et al U.S. Pat. No. 4,119,120, shows a fluid switch having an elastomeric membrane, portions of which may be subjected to fluid pressure to deform or be "inflated" into valve closing positions. MEHAFFEY et al. discloses a system which repeatedly acts against a diaphragm, with fluid as the switching mechanism. Depending on the need, the switching action stops one liquid while allowing another to pass through the piping system. MEHAFFEY et al. does not provide a single action non-repeatable stopper valve. Also, the MEHAFFEY et al. valve does not use a gas as the means for providing pressure to stop fluid flow. Other prior art devices exist in the field of stopper or shutoff valves, yet are merely representative of the general field of valves.
Therefore, it is clear that the prior art devices do not fill the continuing need for an inflatable bladder valve which provides a simple design for quick installation and ease of replacement, yet is inexpensive to manufacture. In addition, a need exists for a valve providing immediate and effective closure in a single action to stop fluid flow in large diameter piping ducts.